Many devices and systems include various numbers and types of sensors. The varied number and types of sensors are used to perform various monitoring and/or control functions. Advancements in micromachining and other microfabrication techniques and associated processes have enabled manufacture of a wide variety of microelectromechanical (MEM) devices, including various types of sensors. Thus, in recent years, many of the sensors that are used to perform monitoring and/or control functions are implemented using MEM sensors.
Various types of MEM sensors have been implemented. For example, accelerometers, gyroscopes, and pressure sensors, just to name a few, have all been implemented using MEM technology. In many instances these MEM sensors includes sensor structures that are configured with relatively small clearance gaps. If small amounts of particulate or moisture were somehow introduced into these small clearance gaps, it could have deleterious effects on MEM sensor operation. Thus, in many instances the MEM sensors include a sealed protective cap that covers the sensor structure, and seals the sensor structure from the surrounding environment.
As is generally known, the pressure at which the sensor structure is sealed can affect its operational characteristics. For example, if the sensor structure for an accelerometer or vibrating gyroscope is sealed at or near atmospheric pressure, it will be overdamped, and if it is sealed at a vacuum, it will be underdamped. It will be appreciated that an overdamped accelerometer is more desirable than an underdamped one, and that an underdamped gyroscope is more desirable than an overdamped one. Thus, the sensor structures for MEM accelerometers are preferably sealed at or near atmospheric pressure, and the sensor structures for MEM gyroscopes are preferably sealed at a vacuum. Other MEM sensors that are preferably sealed at a vacuum include absolute pressure sensors and resonators.
Presently, all MEM sensors (and other types of MEM devices) that are formed on a substrate are sealed at the same pressure. As a result, all of the MEM devices on a single substrate are either overdamped or underdamped. Thus, if a system is being implemented that includes both an overdamped and an underdamped MEM device, the devices would need to be provided from separate substrates, rather than from a single substrate.
Accordingly, it is desirable to provide a method whereby a plurality of MEM devices may be formed on a single substrate and sealed at different pressures. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.